From f2d21425a353728fa69680eff24421cce22981de Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 20 Apr 2023 17:31:58 -0600
Subject: [PATCH] [VarC/subset] Support subsetting VarComposites

By renumbering components.
---
 src/OT/glyf/SubsetGlyph.hh       | 15 +++++++++++++--
 src/OT/glyf/VarCompositeGlyph.hh |  8 ++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/OT/glyf/SubsetGlyph.hh b/src/OT/glyf/SubsetGlyph.hh
index deac1212f..26dc374ea 100644
--- a/src/OT/glyf/SubsetGlyph.hh
+++ b/src/OT/glyf/SubsetGlyph.hh
@@ -46,19 +46,30 @@ struct SubsetGlyph
 
     if (unlikely (!dest_glyph.length)) return_trace (true);
 
-    /* update components gids. TODO: VarComposite. */
+    /* update components gids. */
     for (auto &_ : Glyph (dest_glyph).get_composite_iterator ())
     {
       hb_codepoint_t new_gid;
       if (plan->new_gid_for_old_gid (_.get_gid(), &new_gid))
 	const_cast<CompositeGlyphRecord &> (_).set_gid (new_gid);
     }
+#ifndef HB_NO_VAR_COMPOSITES
+    for (auto &_ : Glyph (dest_glyph).get_var_composite_iterator ())
+    {
+      hb_codepoint_t new_gid;
+      if (plan->new_gid_for_old_gid (_.get_gid(), &new_gid))
+	const_cast<VarCompositeGlyphRecord &> (_).set_gid (new_gid);
+    }
+#endif
 
 #ifndef HB_NO_BEYOND_64K
     auto it = Glyph (dest_glyph).get_composite_iterator ();
     if (it)
     {
-      /* lower GID24 to GID16 in components if possible. TODO: VarComposite. */
+      /* lower GID24 to GID16 in components if possible.
+       *
+       * TODO: VarComposite. Not as critical, since VarComposite supports
+       * gid24 from the first version. */
       char *p = it ? (char *) &*it : nullptr;
       char *q = p;
       const char *end = dest_glyph.arrayZ + dest_glyph.length;
diff --git a/src/OT/glyf/VarCompositeGlyph.hh b/src/OT/glyf/VarCompositeGlyph.hh
index f543eff2b..189122bed 100644
--- a/src/OT/glyf/VarCompositeGlyph.hh
+++ b/src/OT/glyf/VarCompositeGlyph.hh
@@ -71,6 +71,14 @@ struct VarCompositeGlyphRecord
       return StructAfter<const HBGlyphID16> (numAxes);
   }
 
+  void set_gid (hb_codepoint_t gid)
+  {
+    if (flags & GID_IS_24BIT)
+      StructAfter<HBGlyphID24> (numAxes) = gid;
+    else
+      StructAfter<HBGlyphID16> (numAxes) = gid;
+  }
+
   unsigned get_numAxes () const
   {
     return numAxes;